1. Field of the Invention
This invention relates to apparatus for use in combination with a circuit breaker that is capable of moving from an open position to a closed position and more particularly to novel and highly effective apparatus that can be reliably operated by an AC or DC source of power the voltage of which may have any value within a wide range. The apparatus contains sensors that detect conditions that affect the safe operation of the apparatus, and an electronic control circuit prevents operation of the apparatus unless all conditions necessary to its safe operation are satisfied.
2. Description of the Prior Art
Circuit breakers are very important for the safe operation of many electrical circuits. In case of a short circuit or other condition causing circuit overload, a circuit breaker opens, thus interrupting the current and preventing fire or other serious damage. In circuits that carry relatively low currents at relatively low potential, a circuit breaker when tripped can be closed casually, for example by hand. Generally no arcing, or only minor arcing, will occur as the circuit is closed. In contrast, a circuit breaker for a circuit that carries a large current at a high potential cannot be casually closed after it is opened, because severe arcing will result, which will damage the circuit breaker and the portion of the circuit in its vicinity.
Accordingly, it is conventional in such cases to employ powerful springs to close the circuit breaker with great rapidity so that arcing is held to a minimum. These springs can be cocked or charged by means of a charging motor that is connected to the springs through gearing and a cam. Since the circuit controlled by the circuit breaker has been interrupted, the power for the charging motor and a release solenoid that is fired to release the cocked springs must be separately available. A hand-operated jack or pump is usually provided as a back-up to the charging motor. When the springs are fully charged, they are held in the cocked position by a sear that is operated by the release solenoid. When the solenoid is fired, the sear is withdrawn, and the cocked springs are released to close the circuit breaker with great rapidity. Such apparatus for closing a circuit breaker is typically employed in electric power distribution networks at power inputs to factories and other large users of power.
In the prior art, the system for operating the charging motor and the firing solenoid operates from a power supply having predetermined characteristics. For example, the power supply may be 120 VAC, 24 VDC, 48 VDC or 125 VDC. Depending on the power supply available, different internal wiring for the electrical portion of the circuit breaker closing apparatus must be employed. This requires a semi-custom installation, which is relatively expensive.
Moreover, while some interlock features are conventional, there are some unsafe conditions that cannot be detected by conventional apparatus, with the result, for example, that under certain circumstances the charging motor employed to charge the closing springs may continue to run under a condition such that the motor should be stopped. In such a case, damage to the equipment may result.